Make a more complete fix for always supplying an execution context when getting byte sizes from types.

There was a test in the test suite that was triggering the backtrace logging output that requested that the client pass an execution context. Sometimes we need the process for Objective C types because our static notion of the type might not align with the reality when being run in a live runtime.

Switched from an "ExecutionContext *" to an "ExecutionContextScope *" for greater ease of use.

llvm-svn: 228892
diff --git a/lldb/source/DataFormatters/CXXFormatterFunctions.cpp b/lldb/source/DataFormatters/CXXFormatterFunctions.cpp
index 5aa8289..9c45e27 100644
--- a/lldb/source/DataFormatters/CXXFormatterFunctions.cpp
+++ b/lldb/source/DataFormatters/CXXFormatterFunctions.cpp
@@ -317,7 +317,7 @@
         return false;
 
     ClangASTType wchar_clang_type = ClangASTContext::GetBasicType(ast, lldb::eBasicTypeWChar);
-    const uint32_t wchar_size = wchar_clang_type.GetBitSize(nullptr);
+    const uint32_t wchar_size = wchar_clang_type.GetBitSize(nullptr); // Safe to pass NULL for exe_scope here
 
     ReadStringAndDumpToStreamOptions options(valobj);
     options.SetLocation(data_addr);